There are two new photos of a completed clock kit, mounted in an enclosure, and hanging in my dining room. The clock module in the center is 150mm x 150mm, and the enclosure surround is 300mm x 300m craftwood, painted with automotive paint. I think that it looks really great!

I am now able to sell all sorts of components, ranging from complete clocks, through to kits, through to individual modules and components. Please visit my web site www.dougswordclock.com for further information.

I am in Australia, where the mains frequency is 50 Hz (50 cycles per second). This clock uses mains to ensure that it stays accurate. I have realised that people in other countries (USA) may want to construct the clock, so I have modified the firmware to cater for 60Hz countries. Just download either the 50hz, or 60hz firmware depending on where you live.

Another update - I have modified the clock to allow Minute LEDs to be used around the edge - Have a look at the last step of this instructable for details.

I'm wondering about the role given to { D2, D3, R32 } connected to RC0. - Diodes are probably acting as limitator, ok. Then I believe it may be used by the controller to know which part of the sine wave is occuring.

But I can't figure out why this information is needed. could you explain that please ?

The AC input to the bridge rectifier is coupled using R32 to the microprocessor - R32 has been chosen so as to effectively limit the current, so that the voltage excursions (both negative and positive) do not damage the diodes. Using 100K effectively limits the current to tens of microamps.

D2 and D3 act to protect the microprocessor input - The Zener conducts at 5V, preventing the pin from going above 5v, and the 1N914 conducts when the input tries to go negative (remember that it is an AC supply), effectively limiting the voltage to -0.7v Given the massive size of R32, the protection diodes may not be required....

In this version of the circuit, he tells how much time has passed by counting the cycles of the incoming power. It's probably the most accurate of the easy hobbyist timekeeping methods, and doesn't require any expensive components. It does fail when the power is out.

OK i thought this method was too much inaccurate as the frequency varies on the grid with balance between electric supply and demand.

But i assume the variation isn't that much (here in France it goes to approx 50.01 or 49.9 Hz max and mini for a few minutes). As soon as your country grid is stable... It would be interesting to measure the deviation of the clock running with the grid (In the end the mean frequency over a day might be very close to 50 Hz).

I chose to use DS1307 maxim RTC, but i'll rethink the idea in term of cost-effectiveness (too bad i already bought the parts).

Hey. im 15 years old and i'm wanting to make this project at school. I live in New Zealand :) and i'm wondering how much the whole thing costs. I have a budget of $60 nz dollars. p.s useful nz electronic sites are jaycar nz. cheers :)

I have completed the translation of the code for the clock. I only have modified the definitions who were failing. After, I test with PIC Simulater IDE and it's work. Another question. If i implement the minute leds I have to use the 18pin of micocontroler for the led1? there are not problems with the 5v connection that come from the 78L05 to this pin?